(1) Field of the Invention
The present invention relates to a flap ventlid installation assembly, a flap ventlid installation structure, a method for installing the flap ventlid installation assembly, and a mold for molding a tire. More particularly, the present invention relates to a flap ventlid installation assembly including a flap ventlid which can prevent the occurrence of spew (e.g., whisker projections) and burred extensions formed on a tire surface during tire molding to retain the desired initial performance or external appearance of the obtained tire in a satisfactory state and which can be simply installed in the tire mold. Clogging of mold ventholes due to penetration of rubber burrs can also be easily avoided. The present invention relates to a flap ventlid installation structure, a method for installing the flap ventlid installation assembly, and a mold for molding a tire.
(2) Related Art Statement
The molds for molding a tire are often manufactured by casting, which fits for forming complicated shapes conforming to a complicated surface shape designed to have numerous thin projections, such as sharp corners or blades for a tire.
Tire molds manufactured by casting are ordinarily divided into sub-molds, and these sub-molds are combined to form a predetermined whole form at the time of molding the tire. Methods for dividing the mold into sub-molds include a method of cutting the mold into 7-11 sub-molds along the circumference (segmented mold type) and a method of cutting the mold into 2 sub-molds in the direction of the central axis (one cast ring type). These methods can be optionally selected depending on the production conditions, etc.
Molding a tire using a divided mold type is ordinarily performed by compression molding which comprises pressing tire raw material (a green tire) comprising a polymerized rubber material into a mold before molding the application of the design.
In the course of such compression molding, closed spaces (i.e., blockade spaces) are formed between the green tire material and the mold surface on which projections and depressions such as ribs, blades, and the like are formed when the green tire material is pressed into the mold. During molding, air within the blockade spaces is not discharged therefrom, and thus, air bubbles are contained in the finally obtained molded tire. This is a problem in that air bubble defects called xe2x80x9cbearsxe2x80x9d are produced.
Further, after molding, the tire molds should regularly be subjected to inspection and maintenance treatments, including periodic cleanings and the like, since the surface of the mold is roughened due to the adherence of oils and fats and the like during repeated use. Depending on the mold, this cleaning can become troublesome, requiring long cleaning times and expensive equipment. This results in a problem in that the production costs of the articles produced increase.
To prevent the formation of the aforementioned xe2x80x9cbearxe2x80x9d defects, methods of removing air from molds are usually implemented to cope with this situation. For example, as means for removing air from the closed spaces, two types of means have been conventionally employed, one of which is known as a venthole type means and the other is known as a non-spew or slit vent type means.
In methods employing venthole type means, air within blockades is discharged therefrom to the outside through air removal apertures called ventholes that are formed in the mold to lead to the blockades. In this method, the manufacturing costs of the mold are less expensive, and this method has an advantage since one may employ a simple blast method, which comprises blowing media such as glass beads, resin beads, dry ice pellets, and the like to the interior surface of the mold with high-pressure air, for maintenance and inspection purposes. However, spew (whisker projections) is formed on the final molded tire (the tire product) since air is discharged accompanying the outflow of raw tire material (a green tire) into ventholes when the venthole type means is used. This is a disadvantage in that the desired external appearance and initial running performance of the molded tire are deteriorated by the presence of the spew on the final molded tire.
In methods employing a non-spew or slit vent type means, air within blockades is discharged to the outside through gaps formed between sub-molds or slit-like air removal means provided in the predetermined locations. Thus, this method is superior with respect to the external appearance of the final molded tire. Further, there is an advantage in that an adverse effect on the initial running performance is not seen. While the occurrence of spew can be prevented when a non-spew or slit vent type means is employed, however, the formation of burred extensions are not prevented. Further, in the case of this type of a mold, not only is the mold production cost expensive, but there is also a disadvantage in that clogging during molding readily occurs. In addition to the above, with regard to maintenance and inspection, the mold should be broken down into each sub-mold if one employs a simple blast method. Thus, several man-hours are required for cleaning by blasting. Further, since slit portions readily clog with repeated blasting and the contaminants accumulated in slit portions are difficult to remove, special cleaning methods such as chemical cleaning and plasma cleaning should be used. This requires longer cleaning times and introduces expensive equipment, which is a disadvantage in that the production costs of the molded products increase.
As mentioned above, there are respective advantages and disadvantages in these two type means for air removal means. Therefore, at present, one should choose a proper mold, taking into consideration the use of tire to be produced, production costs, and the like. That is, at present, a mold quipped with a non-spew type means is used when serious consideration must be given to the external appearance and the initial performance of a tire, with the acceptance of a relatively expensive production cost. On the other hand, a mold equipped with a venthole type means is used when serious consideration must be given to the production cost of a mold and the costs of molding the tire, with the acceptance of a relatively poor external appearance and relatively poor initial running performance of a finally molded tire. Thus, a satisfactory balance with respect to all the desired aspects, including the external appearance, the initial performance and the production costs of the tire, is sought after.
In light of these circumstances, various types of measures have been proposed. For example, in JP-A-9-11460, a mold that is equipped with air removal lids that are provided in ventholes is provided. The air removal lid is provided with a movable lid insert comprising an axis and a lid head disposed thereon. This lid head is provided with a cavity and a surface having a circular-truncated-cone-shape on the opposite side of the cavity, and is mostly flat on the side near to the cavity. Further, this air removal lid is provided with a casing and is press fit into the venthole together with this casing.
The air removal lid thusly configured has the functions mentioned below. Namely, the lid insert is always pressed to the upper side by means of a spring loaded with force. Moreover, during compression molding using a green tire, the lid insert is pressed down in opposition to the loaded force of a spring by means of pressing the level surface of the lid head into the green tire. During this downward pressing, air can be removed through gaps, that is, air passages, formed between the casing and lid insert. Further, infiltration into air passages of the green tire material can be prevented by interrupting air passages with such contact of the casing and the circular-truncated-cone-shaped surface when compression molding is completed. Furthermore, the lid insert is pushed upwardly again by means of a loaded spring in the cavity during removal of the vulcanized tire from the mold after vulcanization is completed.
Nonetheless, a mold provided with this air removal lid suffers, as mentioned later, from clogging in a relatively high frequency due to the constraints of that structure. The xe2x80x9cleakage distance,xe2x80x9d which is an index for judging the easiness in clogging, defined as xe2x80x9cArea in the Opening and Closing Surface of an Air Removal Lid, and possible defined also as the contact area between the casing and the circular-truncated-cone-shaped surfacexe2x80x9d in the case of the device disclosed in JP-A-9-141660. In other words, the xe2x80x9cdistance from the peripheral portion of the lid opening and closing surface to the holes for air removalxe2x80x9d and the distance from the peripheral portion of the casing to the entrance of air passages in the case of the device disclosed in JP-A-9-141660 cannot be set to be long. In this event, rubber burrs readily teach up into the air removal holes, i.e., air passages, during tire molding. As a consequence, there is such a problem in that the burrs infiltrate into air removal holes and cause clogging. Namely, the constraints are present as a result of the structure since the air removal lid must be embedded inside a tubular casing and stored. To avoid interference in designing, one can not employ a casing having an external diameter in terms of radius of approximately 3 mm or more. In this event, the internal diameter of the casing should be shortened to have a long leakage distance. The radius, however, must be approximately 1.6 mm even at a minimum since the air removal lid is housed in the venthole. Therefore, since there exists the boundary in having a long this leakage distance, clogging occurs readily from rubber burr infiltration into air removal holes (air passages). Thus, this brings a problem in that increased maintenance expenses (i.e., running costs) cannot be eliminated. Moreover, in the case that rubber burrs which have been temporarily infiltrated into the internal area of the air removal holes (air passages) are cut off when the tire is demolded, this would result in a further rise in the probability of the occurrence of clogging. This is because a portion corresponding to the leakage distance is housed in the internal portion of the air removal holes (air passages). Further, there is a problem in that production costs increase due to the numerous parts and complicated structures.
With respect to these problems, the inventors have proposed a flap ventlid which is provided on the tire mold surface side (design surface) of the venthole and which has a lid mechanism wherein when tire is molded by pressing a green tire to the respective surface of a tire mold, air is discharged from blockades, the lid mechanism maintains an open state by spring up until the green tire contacts an upper portion of the mold and air is discharged from the blockades. The degree of spring up of the lid mechanism is reduced during the time when the green tire contacts the upper portion of the lid mechanism to a time when it reaches the surface of sub-molds. Simultaneously, the green tire is prevented from flowing out when the lid mechanism forms a closed state wherein the ventlid intimately contacts the green tire (by dissolving its springing up) when the green tire reaches the surfaces of said sub-molds (Japanese Patent Application No.2001-275807).
By installing the flap ventlid constructed as described above in a tire mold, the occurrence of spew (whisker projections) and burred extensions on a tire surface can be prevented during molding and the obtained tire can have a good initial performance and external appearance, and, at the same time, the tire molding mold production costs per se can be reduced, clogging derived from rubber burr infiltration in ventholes can be effectively prevented and the running costs can be reduced by simplifying maintenance and inspection work.
The object of the present invention is to further improve the above-mentioned flap ventlid and to provide a flap ventlid installation assembly, a flap ventlid installation structure , a method for installing the flap ventlid installation assembly and a mold for molding a tire. The flap ventlid installation assembly can prevent the occurrence of spew (whisker projections) and burred extensions on a tire surface during tire molding and can maintain the desired initial performance and-external appearance of the resulting tire in a satisfactory state and can be simply installed in a tire molding mold, while clogging derived from rubber burr infiltration in air removing holes (ventholes) can be easily avoided.
In order to attain the above objects, the present invention provides the following flap ventlid installation assembly, flap ventlid installation structure flap ventlid installation assembly, installation method, and tire mold.
According to one embodiment of the present invention, a flap ventlid installation assembly is provided for installing a flap ventlid at an opening of an air removing hole (venthole) formed on the design surface of a tire mold. The flap ventlid installation assembly includes a flap ventlid which functions as an opening and closing lid that passes or interrupts the air flow at the opening, and an anchor member. The top portion of the anchor member is connected to the flap ventlid, and the anchor member also has a longer portion which cannot be inserted as it is into the opening of the air removing hole without applying an external force to the longer portion to change the shape into one that is capable of being press fit into the air removing hole through the opening. The flap ventlid can be installed in the opening of the air removing hole of the mold such that at least apart of the flap ventlid contacts the design surface of the tire mold by press fitting (i.e., interference fitting) the anchor member into the air removing hole (hereinafter sometimes referred to as xe2x80x9cthe first inventionxe2x80x9d).
According to another embodiment of the present invention, a f lap ventlid installation assembly is provided for installing a flap ventlid at an opening of an air removing hole (venthole) formed on the design surface of a tire mold. The flap ventlid installation assembly includes a flap ventlid which functions as an opening and closing lid that passes or interrupts the air flow at the opening, and an anchor member having a top portion which is connected to the flap ventlid. The anchor member also has a length dimension that is longer than the depth of the air removing hole. The flap ventlid can be installed in the air removing hole such that at least a part of the flap ventlid contacts the design surface of the tire mold by inserting the anchor member into the air removing hole and bending the end portion of the anchor member that projects from the opening of the air removing hole on the side opposing the design surface at the opening of the air removing hole on the side opposing the design surface (hereinafter sometimes referred to as xe2x80x9cthe second inventionxe2x80x9d).
According to another embodiment of the present invention, a flap ventlid installation structure is provided, in which a flap ventlid, which functions as an opening and closing lid that passes or interrupts the flow of air at an opening of an air removing hole formed on the design surface of a tire mold is provided at the opening of the air removing hole. The flap ventlid installation assembly according to the first invention is installed such that at least a part of the flap ventlid contacts the design surface of the tire mold by press fitting the anchor member into the air removing hole (hereinafter sometimes referred to as xe2x80x9cthe third inventionxe2x80x9d).
According to another embodiment of the present invention, a flap ventlid installation structure is provided in which a flap ventlid, which functions as an opening and closing lid that passes or interrupts the air flow at an opening of an air removing hole formed on the design surface of a tire mold, is provided at the opening of the air removing hole. The flap ventlid installation assembly according to the second invention is installed such that at least a part of the flap ventlid contacts the design surface of the tire mold by inserting the anchor member into the air removing hole and bending the end portion of the anchor member that projects from the opening of the air removing hole on the side opposing the design surface at the opening of the air removing hole on the side opposing the design surface (hereinafter sometimes referred to as xe2x80x9cthe fourth inventionxe2x80x9d).
According to a first aspect of the present invention, a flap ventlid installation structure according to the third or fourth inventions is provided, wherein the flap ventlid installation assembly is installed such that when the flap ventlid installation assembly is drawn out from the air removing hole, the anchor member rakes out foreign matter, such as tire molding material debris or rubber burrs, present in the air removing hole.
According to a second aspect of the present invention, the flap ventlid installation structure according to the first aspect is provided, wherein the anchor member has a projection for raking out the foreign matter.
According to a third aspect of the present invention, the flap ventlid installation structure according to the first or second aspects is provided, wherein the anchor member is made of a material to which the foreign matter present in the air removing hole readily adheres or such a material is coated on a surface of the anchor member.
According to a fourth aspect of the present invention, the flap ventlid installation structure according to any of the first to third aspects is provided, wherein the material is copper or a copper alloy.
According to yet another embodiment of the present invention, a method for installing a flap ventlid, which functions as an opening and closing lid that passes or interrupts the air flow at an opening of an air removing hole formed on the design surface of the mold is provided. The anchor member of the flap ventlid installation assembly according to the first invention is press fit into the air removing hole through the opening so that at least a part of the flap ventlid contacts the design surface of the tire mold, thereby installing the flap ventlid (hereinafter sometimes referred to as xe2x80x9cthe fifth inventionxe2x80x9d).
According to another embodiment of the present invention, a method for installing a flap ventlid, which functions as an opening and closing lid that passes or interrupts the air flow at an opening of an air removing hole formed on the design surface of a tire mold, is provided. The flap ventlid installation assembly according to the second invention is installed such that at least a part of the flap ventlid contacts the design surface of the tire mold. The method comprises the steps of inserting the anchor member into the air removing hole and bending the end portion of the anchor member that projects from the opening of the air removing hole on the side opposing the design surface at the opening of the air removing hole on the side opposing the design surface (hereinafter sometimes referred to as xe2x80x9cthe sixth inventionxe2x80x9d).
According to a fifth aspect of the present invention, a method for installing a flap ventlid according to the fifth or sixth inventions is provided, wherein the flap ventlid installation assembly is installed such that when the flap ventlid installation assembly is drawn out from the air removing hole, the anchor member takes out foreign matter present in the air removing hole.
According to a sixth aspect of the present invention, a method for installing a flap ventlid according to the fifth aspect is provided, wherein the anchor member has a projection for raking out the foreign matter.
According to a seventh aspect of the present invention, a method for installing a flap ventlid according to the fifth or sixth aspects is provided, wherein the anchor member is made of a material to which the foreign matter present in the air removing hole readily adheres or such a material is coated on the surface of the anchor member.
According to an eighth aspect of the present invention, the method for installing a flap ventlid according to fifth, sixth or seventh aspects is provided, wherein the material is copper or a copper alloy.
According to another embodiment of the present invention, a mold for molding a tire, which is provided with a flap ventlid installation structure according to the third or fourth inventions or the first through fourth aspects, is provided (hereinafter sometimes referred to as xe2x80x9cthe seventh inventionxe2x80x9d).